Significant behavioral symptomatology, including sleep disruption, nocturnal wanderings, restlessness and daytime sleepiness are frequent health complaints in the elderly. Such behavioral changes severely hinder the quality of life of the elderly and are a major reason for institutionalization. Alterations in circadian rhythmicity are also common in old age and consist of a dampening of amplitude and an advanced phase of both physiological and behavioral variables thought to be regulated by a central neural circadian pacemaker. In humans, bright light and social cues have been shown to synchronize circadian rhythms. In the elderly, exposure to bright light and social cues is markedly diminished when compared to young adults. Absence of professional constraints, decreased mobility due to physical ailments, reduced socialization and outdoor activities are hallmarks of old age. These reductions in environmental zeitgebers are most marked in nursing homes. The objective of the present proposal is to test the hypothesis that enforcement of a structured bright light-dark cycle and/or a structured social and activity schedule will result in an increase in the amplitude and reorganization of circadian rhythms, as evidenced by consolidation of nocturnal sleep and improvement of daytime functioning. All subjects will be studied in the assisted living facilities for 10 days before treatment and during 14 days of treatment with either a structured bright light/dark cycle, structured activity and social programs or a combination of the two. The bright light-dark cycle will consist of exposure to total darkness from 2300 to 0700, exposure to bright (1,000 to 10,000 lux) in the late morning (0900-1100) and evening (1900-2100) and exposure to dim light (<200 lux) for the remainder of the 24-hour cycle. The schedule of physical and social activities will include fixed bedtimes and mealtimes, two one-hour sessions of recreational physical activity in group, one hour of supervised exercise, one hour of social activities in group and two periods of free time where the subjects will be monitored to prevent naps. A control group will be exposed to schedule dim light. The rest-activity cycle and light exposure will be monitored continuously via ambulatory monitors during each of the studies. In addition, subjects will be submitted to two consecutive days of study before treatment and after treatment. During these two days, the circadian rhythm of core body temperature will be monitored continuously, and tests of alertness and performance will be administered at hourly intervals during the day. Sleep will be polygraphically monitored using a portable system.